Energy Converter - Joules, Calories, kWh & BTU Calculator
⚡ Physics & Nutrition

Energy Converter

The ultimate unit conversion tool for work and heat. Convert accurately between Joules (SI), Kilowatt-hours (Electricity), Calories (Food), and BTUs (Heating).

Energy Engine

Enter energy value to convert.

🔋 Energy Amount
🎯 Decimal Precision
CONVERTED ENERGY
0.0002
Kilocalories (kcal)
Conversion Factor:
1 J ≈ 0.000239 kcal
Kilojoules 0.001 kJ
🔥
Calories (cal) 0.239 cal
💡
Watt-hours 0.0003 Wh

The Calorie Confusion: cal vs kcal

[Image of food nutrition label]

In nutrition, when we say "Calories" (with a capital C), we actually mean **Kilocalories (kcal)**. This is 1,000 times larger than the small calorie (cal) used in chemistry.

🍎
Food Calorie (Cal)

Equal to 1 kcal (1000 small calories). This is what you see on food labels. Equal to 4,184 Joules.

🧪
Small calorie (cal)

The energy needed to heat 1 gram of water by 1°C. Equal to 4.184 Joules.

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Joule (J)

The standard SI unit. Food packaging in Europe and Australia lists energy in kJ (Kilojoules).

Energy Conversion Formulas

Conversion Multiplier Reverse
kcal to Joules × 4,184 ÷ 4,184
kWh to Joules × 3,600,000 ÷ 3,600,000
BTU to Joules × 1,055.06 ÷ 1,055.06
Foot-pound to Joules × 1.3558 ÷ 1.3558

Understanding Kilowatt-hours (kWh)

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Electricity Bills

You are billed in kWh. 1 kWh is the energy used by a 1,000 Watt appliance running for 1 hour. It equals 3.6 Megajoules.

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EV Batteries

Electric Vehicle battery capacity is measured in kWh. A typical EV has a 60-100 kWh battery.

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Power vs. Energy

Don't confuse kW (Power, rate of flow) with kWh (Energy, total amount). kW is like speed; kWh is like distance.

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Frequently Asked Questions

How many Joules in a Calorie?
There are approximately 4.184 Joules in 1 small calorie. There are 4,184 Joules (or 4.184 kJ) in 1 food Calorie (kcal).
What is a BTU?
BTU stands for British Thermal Unit. It is the energy needed to heat 1 pound of water by 1°F. It is commonly used to rate Air Conditioners and Heaters.
How do I convert kJ to Calories?
Divide the Kilojoules by 4.184 to get food Calories (kcal). For example, 8400 kJ is approx 2000 kcal (standard daily intake).
What is an Electronvolt (eV)?
An Electronvolt is a tiny unit of energy used in particle physics. It is the energy gained by an electron accelerating through 1 volt. 1 eV ≈ 1.602 × 10^-19 Joules.
Why do air conditioners use tons?
A "Ton of Refrigeration" is a power unit based on energy. It is the rate of heat removal needed to freeze 1 short ton of water in 24 hours. 1 Ton ≈ 12,000 BTU/hour.
Is 1 kWh a lot of energy?
It can power a 100-Watt lightbulb for 10 hours, or run an electric car for about 3-4 miles.
What is the SI unit of energy?
The Joule (J) is the standard SI unit for energy, work, and heat.
How many Joules in 1 Foot-Pound?
1 Foot-Pound (ft⋅lbf) is approximately 1.356 Joules. This unit is often used in the US for torque and work measurements.
Can energy be negative?
In general physics terms, kinetic energy is always positive. Potential energy can be negative depending on the reference point (like gravity wells).
How precise is this tool?
It uses high-precision floating point math with standard conversion factors (e.g., 1 cal = 4.184 J exactly) to ensure scientific accuracy.